Leak-resistant dry cell



Dec. 14, 1965 'r. A. REILLY ETAL 3,223,557

LEAK-RES I S TANT DRY CELL Filed May 1. 1961 INVENTORS THOMAS A. REILLY JOHNSON R. BECKMAN HARRY K. BIS OP 8% A T TORNEV United States Patent 3,223,557 LEAK-RESESTANT DRY CELL Thomas A. Reilly, Johnson R. Beekman, and Harry K. Bishop, Cleveland, Ohio, assignors to Union Carbide Corporation, a corporation of New York Filed May 1, 1961, Ser. No. 106,764 The portion of the term of the patent subsequent to May 21, 1980, has been disciaimed 7 Claims. (Cl. 136133) This invention relates to leak-resistant dry cells of the type having a closed container surrounding the cell proper.

The so-called LeClanche dry cell used for flashlights, portable radios, photoflash and other devices has gone through an evolution of improvements during the past decade or more in an attempt by manufacturers to prevent leakage from the cell during and after its use. Despite the many proposals, however, that have been advanced, there still remains a need for a better leak-resistant dry cell.

One proposal that has been adopted commercially is to encase a conventional dry cell within a closed container. This dry cell construction, however, has been plagued by certain difliculties. For example, one type of container which has been used comprises a metal container, but this suffers from the disadvantage that the metal is subject to corrosion by liquid exudate from the cell. To avoid this disadvantage, non-corrodible containers have also been utilized. The principal difl'iculty, however, with non-corrodible containers is that they do not possess the mechanical strength of metal containers and suffer from the disadvantage that they may often be damaged, and even destroyed, by the pressure which builds up from the formation of gas within the cell. Several suggestions have been advanced for overcoming this disadvantage of noncorrodible containers in which the attempt has been made to continuously vent the gas from the cell. Thus, in prior constructions, the gas has been vented, for example, through the carbon electrode, and then out through venting means provided in the top closure of the container. The difficulty, however, with these suggestions is that the venting paths, for instance through the carbon electrode, have been prone to obstruction by cell exudate, thereby blocking the passage of gas from the cell.

In addition to obstructing the venting paths provided in the cell, this cell exudate has also given rise to other serious problems. For example, one difficult problem has been the tendency for metal formed in solution by normal consumption of the metal electrode to deposit out from the cell exudate in the form of spongy tree-like deposits. These metal deposits have formed principally on top of the depolarizer mix between the electrodes of the cell and have been particularly troublesome from the standpoint of cell performance, for they very likely can short out the cell by establishing short-circuit paths between the cell electrodes. Thus, the cell in many instances may be drained of its power even though it is not in use.

It is therefore an important object of the invention to provide an improved gas venting path in a leak-resistant dry cell of the type having a non-corrodible container, which gas venting path is not prone to obstruction during use of the cell.

More specifically, it is another object to provide such a gas venting path in a leak-resistant dry cell while at the same time preventing the establishment of short-circuit paths between the electrodes of the cell.

Patented Dec. 14, 1965 ice Still another object is to provide such a gas venting path in a leak-resistant dry cell particularly of the type of construction utilizing a non-metallic jacket having locked thereto a metallic bottom closure, in which the jacket is protected against liquid penetration and in which the bottom closure is protected against corrosion.

Briefly, these and other objects are achieved by the invention which comprises a tubular shaped partition seal positioned between the top closure and depolarizer mix of a leak-resistant dry cell. The tubular shaped partition seal has an outwardly flanged upper end locked in engagement between the top closure and a non-metallic jacket and a lower end embedded within the depolarizer mix defining a barrier which protects the carbon electrode of the cell from contact by liquid cell exudate and also providing a path for venting gas from the cell. The jacket for the cell is provided with a liquid-proof liner and also has locked to it a metallic bottom plate. The bottom plate is protected against corrosion by a shield positioned within the lower edges of the jacket. Both the juncture between the partition seal and the jacket liner at the top of the cell and the juncture between the shield and the jacket liner at the bottom of the cell are hydrophobic, this characteristic being obtained preferably by forming these parts of hydrophobic plastics.

In the accompanying drawing:

FIG. 1 is a vertical section of a leak-resistant dry cell embodying the invention; and

FIG. 2 is a greatly enlarged detail view of the top portion of the dry cell shown in FIG. 1.

Referring to the drawing, a leak-resistant dry cell of a construction otherwise conventional but embodying the invention is shown in FIG. 1. The cell comprising a cup electrode 10 of a consumable metal, for instance, zinc, containing therein a central electrode 12 of porous carbon embedded within a depolarizer mix 14 and an immobilized electrolyte 16 suitably in the form of a conventional paste, is provided with a jacket 18 having locked thereto a metallic bottom plate 20 and a top cover plate 22 having therein a vent 24. At the top of the cell between the top cover plate 22 and the depolarizer mix 14 and so placed as to define an inner free space 26 around the carbon electrode 12 and an outer exudate chamber 28 is a partition seal comprising a tubular shaped member 30, the upper end of which is flanged outwardly and locked in engagement between the top cover plate 22 and the jacket 18 as best shown in enlarged detail in FIG. 2. The lower end of the tubular shaped member 30 is embedded within the depolarizer mix 14 at the junction 32. The tubular shaped member 30 preferably is molded from a plastic material, for example, polyethylene. The construction for the dry cell described also utilizes a shield for the bottom plate 20 comprising a plastic disclike cover 34 whose outer peripherial edges are locked in engagement between the bottom plate 20 and the jacket 18. This type of construction protects the bottom plate 20 against corrosion and also utilizes a metallic rivet 36 positioned within the disc-like cover 34 for making electrical contact between the cup electrode 10 and the bottom plate 20. The rivet 36 preferably is composed of a non-corrodible and non-consumable type of a metal such as, for example, titanium, chromium or lead as substantially disclosed and claimed in our copending application, Serial No. 106,163, filed concurrently herewith, and now United States Patent No. 3,115,429 issued on December 24, 1963.

The jacket 18 is of a non-corrodible type preferably composed of a bibulous paper, for instance, kraft paper and has provided to its inner surfaces a liquid-proof liner 38 preferably composed of a plastic film, for example, polyethylene terephthalate as shown in enlarged detail in FIG. 2. This construction conveniently lends itself to incorporating the liquid-proof liner 38 by spiral Winding techniques during manufacture of the jacket 18. The liquid-proof liner 38 may also be incorporated by adhesively bonding it to the interior of the jacket 18 after the latter has been manufactured. The jacket 18 fits the cup electrode ll) rather loosely, thereby providing a supplementary chamber 40 for receiving liquid exudate from the cell during its use.

Having described the construction of a dry cell embodying the invention, its mode of operation may now be visualized. During use of the cell, especially under severe conditions, gas is released. The gas follows a path through or around the carbon electrode 12 in the depolarizer mix 14, into the free space 25, and through the electrode 12, or directly through the electrode 12 from within the depolarizer mix 14, and then out of the cell through the vent 24 in the top cover plate 22 or from between the locked engagement of the top cover plate 22 and the jacket 18. At the same time, liquid is exudated through the depolarizer mix 14 towards the cup electrode and eventually collects within the exudate chamber 28 but is barred from entering the free space 26 by the tubular shaped member 30. The junction 32 provides a barrier which effectively blocks ofi liquid from creeping into the free space 26 over the top surface of the depolarizer mix 14. Thus, it will be seen by this construction that liquid exudate is not only barred from blocking the passage of gas through the free space 26 and carbon electrode 12 or from escaping out of the cell by way of the free space 26, but also is barred from establishing short-circuit paths between it and the cup electrode 10 by the deposition of spongy zinc metal over the depolarizer mix 14. This construction also takes advantage of an insoluble salt layer which normally forms over the surfaces of the depolarizer mix 14 during discharge for providing a seal around the junction 32 which liquid exudate cannot penetrate.

Another important feature of the invention is the provision of an effective liquid-tight top and bottom closure for the cell. In prior dry cell constructions, the top cover plate and bottom plate of the closures have been locked together with the jacket for the purpose of prohibiting leakage of liquid but at the same time permitting the escape of gas from the cell. This type of construction depends largely upon the mechanical tightness of the locked junction for its effectiveness, which may often be destroyed or lost during use of the cell, for example by damage to the cell container whereby leakage of liquid ensues. In the presentconstruction, both the tubular partition seal and the disc-like cover for the bottom plate are curled and locked at their peripheral edges within the top and bottom closures in juxtaposition to the liquidproof liner for the jacket. These juxtaposed members preferably being composed of hydrophobic plastic materials provide top and bottom closures for the cell which bar the passage of liquid but permit pressure-relieving venting of gas.

A number of dry cells embodying the invention have been made and tested over a wide range of conditions. These tests demonstrated the effectiveness of the invention, for cells otherwise identical in construction but lacking the structural features of the invention showed evidence of leakage from and/ or bulging of the cell container while those cells embodying the invention showed little or no evidence of gas pressure build-up and consistently demonstrated superior leakproofness. The effectiveness of the invention was further demonstrated by the fact that the dry cells of the invention had a longer life and did not short-out during the tests.

It will be understood that many changes and modifications of the dry cell construction described herein may 4. be made without departing from the spirit and scope of the invention.

Suitable hydrophobic materials for use in the invention include, in addition to those mentioned above, vinyl resins, polyethylene, polypropylene, styrene resins, and waxes. If a wax is used in a hydrophobic joint, a plastic should be used with it.

We claim:

1. A leak-resistant dry cell comprising, in combination, a cup electrode of a consumable metal containing depolarizer mix, electrolyte and a central carbon electrode embedded within said depolarizer mix; a non metallic jacket having a liquid-proof liner embracing said cup electrode; a metallic top closure and bottom plate locked to said jacket, said top closure having gas venting means therein; a substantially tubular shaped member positioned between said top closure and said depolarizer mix having an outwardly flanged upper end locked in engagement between said top closure and said jacket, said tubular shaped member surrounding said carbon electrode and providing a free space therebetween and an exudate chamber surrounding said tubular shaped member and defining a barrier which protects said carbon electrode from contact with liquid exudate from said cell, said tubular shaped member being embedded within said depolarizer mix and forming a juncture which prohibits the passage of said liquid exudate beneath said member and into said free space, said tubular shaped member in conjunction with said gas venting means in said top closure providing a path for venting gas from said cell; a disc-like shield for said bottom plate positioned below said cup electrode; and an electrical contact element positioned within said disc-like shield and making electrical contact between said cup electrode and said bottom plate.

2. A leak-resistant dry cell as defined by claim 1 in which said disc-like shield is locked in engagement between said bottom plate and said jacket.

3. A leak-resistant dry cell as defined by claim 1 in which said electrical contact element is non-corrodible and non-consumable.

4. A leak-resistant dry cell as defined by claim 1 in which said liquid-proof liner for said jacket is composed of a plastic film.

5. A leak-resistant dry cell as defined by claim 1 in which said tubular shaped member is composed of a plastic material.

6. A leak-resistant dry cell as defined by claim 1 in which said tubular shaped member, disc-like shield and liquid-proof liner for said jacket are composed of hydrophobic materials.

7. A leak-resistant dry cell comprising, in combination, a cup electrode of a consumable metal containing depolarizer mix, electrolyte and a central carbon electrode embedded within said depolarizer mix; a non-metallic jacket having a liquid-proof liner embracing said cup electrode; a metallic top closure and bottom plate locked to said jacket, said top closure having gas venting means therein; and a substantially tubular shaped member positioned between said top closure and said depolarizer mix having an outwardly flanged upper end locked in engagement between said top closure and said jacket, said tubular shaped member surrounding said carbon electrode and providing a free space therebetween and an exudate chamber surrounding said tubular shaped member and defining a barrier which protects said carbon electrode from contact with liquid exudate from said cell, said tubular shaped member being embedded within said depolarizer mix and forming a juncture which prohibits the passage of said liquid exudate beneath said member and into said free space, said tubular shaped member in conjunction with said gas venting means in said top closure providing a path for venting gas from said cell.

(References on following page) References Cited by the Examiner UNITED STATES PATENTS Urry 136-133 Jammet 136-133 Reilly et a1 136--107 Urry 136-107 6 FOREIGN PATENTS 1,216,672 11/ 1959 France. 1,239,964 7/ 1960 France.

859,230 1/ 1961 Great Britain.

JOHN H. MACK, Primary Examiner.

JOHN R. SPECK, Examiner. 

1. A LEAK-RESISTANT DRY CELL COMPRISING IN COMBINATION, A CUP ELECTRODE OF A CONSUMABLE METAL CONTAINING DEPOLARIZER MIX, ELECTROLYTE AND A CENTRAL CARBON ELECTRODE EMBEDDED WITHIN SAID DEPOLARIZER MIX; A NONMETALLIC JACKET HAVING A LIQUID-PROOF LINER EMBRACING SAID CUP ELECTODE; A METALLIC TOP CLOSURE AND BOTTOM PLATE LOCKED TO SAID JACKET, SAID TOP CLOSURE HAVING GAS VENTING MEANS THEREIN; A SUBSTANTIALLY TUBULAR SHAPED MEMBER POSITIONED BETWEEN SAID TOP CLOSURE AND SAID DEPOLARLZER MIX HAVING AN OUTWARDLY FLANGED UPPER END LOCKED IN ENGAGEMENT BETWEEN SAID TOP CLOSURE AND SAID JACKET, SAID TUBULAR SHPAED MEMBER SURROUNDING SAID CARBON ELECTRODE AND PROVIDING A FREE SPACE THEREBETRWEEN AND AN EXUDATE CHAMBER SURROUNDING SAID TUBULAR SHAPED MEMBER AND DEFINING A BARRIER WHICH PROTECTS SAID CARBON ELECTRODE FROM CONTACT WITH LIQUID EXUDATE FROM SAID CELL, SAID TUBULAR SHAPED MEMBER BEING EMBEDDED WITHIN SAID DEPOLARIZER MIX AND FORMING A JUNCTURE WHICH PROHIBITS THE PASSAGE OF SAID LIQUID EXUDATE BENEATH SAID MEMBER AND INTO SAID FREE SPACE, SAID TUBULAR SHPAED MEMBER IN CONJUNCTION WITH SAID GAS VENTING MEANS IN SAID TOP CLOSURE PROVIDING A PATH FOR VENTING GAS FROM SAID CELL; A DISC-LIKE SHIELD FOR SAID BOTTOM PLATE POSITIONED BELOW SAID CUP ELECTRODE; AND AN ELECTRICAL CONTACT ELEMENT POSITIONED WITHIN SAID DISC-LIKE SHIELD AND MAKING ELECTRICAL CONTACT BETWEEN SAID CUP ELECTODE AND SAID BOTTOM PLATE. 